Making Metal Clay, Paste, and Slip

You can create your own metal clay (also known as “lump” metal clay),
paste, slip, or oil paste.
You can also add ingredients to your metal clay to modify its properties; or to
make it better suited for a particular use.
This page contains information about metal clay ingredients and links to metal
clay recipes.

Types of Metal Clay

Metal clays made from the same metal (such as silver) can usually be used together
to make one piece.
The piece should be fired at the highest temperature required for any of the mixed
clays.
If the clays have different shrinkage rates, the piece may warp when it is fired.

Some types of metal clay contain different ingredients than others, and while most
of these can still be used together in one piece (so they are touching), some should
not be mixed together to make a single lump of clay or clay paste.

Lump Metal Clay

This is the typical, common type of metal clay.
It is the thickest kind, and looks and feels like a lump of clay.

Slip and Paste

The terms “slip” and “paste” can be used interchangeably.
Paste is a more liquid version of metal clay.
Paste is used to add details or texture, or to attach
greenGreen pieces have not been fired.
metal clay pieces together.
The metal clay pieces may be wet or dry.
You can make your own paste from metal clay.

To create paste, add a small amount of water to the metal clay.
You can also add a bit of vinegar to prevent mold.
Note that bronze paste can eventually separate with the tin rising to the top,
creating a dark surface layer; this should be stirred in.

Note: This is not the same as oil paste.

Paste Syringe

It is difficult to make your own paste syringe.
The paste can be mixed as usual, though it will require some experimentation to find
the best consistency.
The paste should be mixed as thoroughly as possible, so it is all of the same
consistency.
One difficulty lies in filling the syringe with the metal clay paste, without
creating air bubbles.
Note that the syringe should not have any metal parts that touch the clay, unless
you know that the metal will not react with the clay.

Oil Paste

This is often called “Lavender Oil Paste.”
Oil paste is used to attach metal clay pieces that have already been fired, or to
repair broken or cracked fired pieces.
You can make your own oil paste from homemade or purchased metal clay.

Note: Do not use Art Clay Oil Paste on unfired clay, or mix Art Clay Oil Paste with
unfired metal clay or paste.
It contains a different kind of binder that is incompatible with unfired clay.
Homemade oil paste is compatible with unfired metal clay.

Most people use lavender oil to make oil paste.
However, other essential oils can be used.
Olive oil works; some have tried citrus (orange, lemon, tangerine) and peppermint.
Apparently tea tree oil doesn't work as well as lavender.

To make lavender oil paste, add a few drops of tincture of lavender oil (which
contains essential oil, alcohol, and water) to metal clay.
If you have pure essential oil, which is more concentrated, use less oil and
add water or alcohol.
You want to create a thick, spreadable paste.
A little glycerin may help make it creamy; a little rubbing alcohol can make it
more workable.
After mixing, let it sit overnight.
Add a little distilled water if the paste is too thick.

Metal Clay Sheet/Paper

Metal clay is also available as a sheet or paper.
This is thin and flexible metal clay.
Since it is thin and delicate, it is often used to add pieces to other metal clay.
It can also be used for origami or woven pieces.
Pieces made only from sheet clay cannot be fired with a torch.

Do not add water to metal clay sheet; it will fall apart.
You can use a small amount of water to glue the sheet to a piece of metal clay.

Purchased metal clay sheet uses a different type of binder than the lump clay, and
should not be mixed with regular clay.

Note: Metal clay paper is a variety of metal clay.
Paper clay is an entirely different clay made of paper, not metal.

Ingredients, Additives, or Modifiers

These are some of the ingredients that can be used to make metal clay or additives
that can be mixed into packaged metal clay.
Some of these ingredients may not be readily available in your area.
Generally only natural or organic ingredients should be added to metal clay, or used
on your hands when working with the clay.
Artificial ingredients can affect the workability of the clay and may not burn out
when the clay is fired.

Some metals are much stronger than others.
The stronger metals will be more forgiving of less-than-ideal mixtures, since
weak metal clay will still be strong enough for most purposes.
Adding ingredients to metal clay may also affect its shrinkage rate.

When making your own metal clay or mixing from metal clay powders, the water should
be sprayed onto the powder.
Add the water gradually.
After the clay starts forming lumps, the clay can be mixed together.
If you add too much water, you can spread it out and let some of the water evaporate.

Oil and Essential Oil

Many people add olive oil to metal clay.
The oil slows drying and improves the workability of the clay.
Other oils may work as well.
Do not add too much oil to the clay; it makes the clay unworkable and unusable.
Too much oil may also reduce the strength of the finished piece.

Lavender oil is often used to make “oil paste” for fixing fired pieces
that are broken or have cracks.
Oil paste is also used to attach fired pieces to each other.
The lavender oil smells nice, but other essential oils can also be used.

Glycerin

Glycerin can be produced from plants or animal fat.
Vegetable source glycerin is safe to eat.

Glycerin makes the clay more workable, and slows the drying time.
If you add enough glycerin, the metal clay will remain flexible even when dry.
Adding too much glycerin may reduce the strength of the finished piece.

Vinegar

After clay has been mixed or opened, a few drops of vinegar will prevent it from
developing mold.

Metal Powder

Metal powder used to make metal clay should contain very small particles—no
larger than 20 microns in size.
Many commercial metal clays have particles between 1 and 20 microns.
The size of the metal particles affects the firing temperature and time, as well as
the strength of the finished piece.
Different sizes of particles may be combined—this helps fill some of the
empty spaces between the particles.

The metal particles may be spherical (round) or flakes.
Flakes may make the clay softer and easier to work with, but reduce the strength.
The original Silver PMC uses flakes.

CMC (Carboxy Methyl Cellulose)

CMC powder is a cellulose product used as a binder.
Cellulose is obtained from green plants, such as wood pulp or cotton, and is the
main ingredient in cardboard and paper.
CMC is available from pottery or bakery stores.
Other cellulose powders would probably work as well.

Peridur Powder

This is one brand of CMC.

Polyolefin Powder

Polyolefin powder is not a natural product, it is synthetic.
It is used for car covers and seat cushions.
Polyolefin burns relatively cleanly, and produces heat at a fast rate.
This may help with sintering.

Note: Most commercially available metal clays use only organic ingredients
for binder.

Starch

Starch can be used as a binder.
Cornstarch (also called corn flour in some countries) and wheat flour can be used
to make metal clay.
Besides cornstarch and regular flour, you might experiment with rice starch and
potato starch.
The ideal binder is finely ground so that it has small particles, and burns
relatively cleanly.

Other Ingredients

Wax, gum, agar, resin, and propylene glycol have also been mentioned as
possible ingredients for metal clay.

Petroleum jelly and mineral oil are not recommended.
Petroleum can degrade the binder.
Do not use a petroleum-based product on your hands before working with clay.

Making Metal Clay

Making your own metal clay is certainly more difficult than buying ready-made clay
or clay powder, and requires dedicated equipment.
Some of the ingredients may have to be purchased in large quantities.
Note that even non-toxic ingredients can be dangerous if not handled
properly—consider buying metal clay powder instead of trying to make
your own.

These recipes were created from experimentation.
It is likely they contain different ingredients than metal clays that can be
purchased.
Because of this, the properties of homemade metal clay will probably differ from the
commercially available versions.
Note that the commercial versions have been extensively researched and tested, and
will likely produce more consistent results than do-it-yourself (DIY) metal clay.

The workability and drying rate of the clay depend on the ingredients and
mixing process.
You can fabricate metal clay in an aerosol mixer or a household blender.
Metal clay should be easily worked when wet, easily carved when dry, and strong
when fired.
To create a strong metal clay:

Use small metal particles, and a mix of sizes.

Use small binder particles.

Use as little binder and oil as possible, while still keeping the clay
workable.

All additives should burn cleanly, and ideally be organic/natural.

The metal clay cannot be contaminated with other metals.

A bad batch of homemade metal clay may not
sinterSintering makes a solid object by heating
powder without melting. properly.
If it does sinter, it may not be very strong.
You may have to experiment with different ingredients and firing schedules for your
homemade metal clay.
Firing hotter and longer will make stronger clay, but you must stay below the
melting point of the metal.

Safety

Follow proper safety procedures.
Though the ingredients used in metal clay may be non-toxic, the powders can be
dangerous to inhale.

Work in an area with good ventilation.

When working with these powders, you must wear the correct dust mask.
The particles are small and can be inhaled.

Items used for making the metal clay, such as a blender, should not be used for
food.

Do not mix metal clay near food or food preparation areas.

To avoid getting the powders in your eyes, wear goggles.

Some of the ingredients may be irritating; wear gloves when handling the
powders.

Be aware that these powders can also get on your clothes.

If you have a fume hood (lab equipment, not the fan above your stove),
use it when mixing the metal clay.

In the United States, Material Safety Data Sheets (MSDS) contain information on
the safety of various substances.
These are available in other countries as well; MSDSs are country-specific.
Check the MSDSs of any unknown ingredients before purchase.
Note that products from different suppliers may contain different ingredients and
have different MSDSs.

If you use any ingredients that are not organic, be sure you know what chemicals
are produced when they are burned.
Never breathe the fumes produced when firing any metal clay, even if all
ingredients are organic.

Shrinkage

The percentage of metal clay shrinkage depends on the size of the metal particles
and the particles in the binder, and the amount of binder in the clay.
If you are using ingredients from your kitchen, the particle sizes are unknown; and
may vary from one batch to another.
You may not get consistent results when making your own metal clay.

Mixing

The order of mixing can make a difference in the success of your metal clay.
This is the recommended order:

Dry binder ingredients

Metal powder

Wet ingredients: Water, oil, glycerin

Metal Clay Recipes

All of these metal clay recipes can probably be modified for bronze, copper, silver,
or gold clay.

A recipe for bronze clay from Del Feast may be found at
Metal Clay
Academy: Make Your Own Metal Clay.
It uses easily available ingredients, but after it has been fired it may not be as
strong as the commercial versions of clay.
Don't try to make thin pieces from this clay until you have tested its strength.

Note: Follow proper safety procedures.
When working with these powders, you must wear the correct dust mask.
Items used for making the metal clay should not be used for food.

These are the ingredients used for a “kitchen” version of do-it-yourself
bronze clay:

Bronze powder

Plain flour

Corn flour (known as cornstarch in the United States)

Olive oil (or other organic oil)

Water

Bronze powder contains mostly copper.
The remaining ingredients are natural/organic, so will burn out when the clay is
fired.

Other, similar ingredients will also work—he has also experimented with rice
starch instead of wheat, with excellent results.
Make sure than all ingredients have a small particle size.